Surgical cassette for intraocular pressure control

ABSTRACT

An improved surgical cassette for controlling intraocular pressure during ophthalmic surgery.

FIELD OF THE INVENTION

The present invention generally pertains to microsurgical systems andmore particularly to controlling intraocular pressure in ophthalmicsurgery.

DESCRIPTION OF THE RELATED ART

During small incision surgery, and particularly during ophthalmicsurgery, small probes are inserted into the operative site to cut,remove, or otherwise manipulate tissue. During these surgicalprocedures, fluid is typically infused into the eye, and the infusionfluid and tissue are aspirated from the surgical site.

Maintaining an optimum intraocular pressure during ophthalmic surgery iscurrently problematic. When no aspiration is occurring, the pressure inthe eye becomes the pressure of the fluid being infused into the eye.This pressure is typically referred to as the “dead head pressure”.However, when aspiration is applied, the intraocular pressure dropsdramatically from the dead head pressure due to all the pressure lossesin the aspiration circuit associated with aspiration flow. Therefore,ophthalmic surgeons currently tolerate higher than desired dead headpressures to compensate for occasions when aspiration would otherwiselower the intraocular pressure to soft-eye conditions. Clinically, suchover-pressurizing of the eye is not ideal.

Accordingly, a need continues to exist for improved apparatus forcontrolling intraocular pressure during ophthalmic surgery.

SUMMARY OF THE INVENTION

In one aspect, the present invention is a surgical cassette including adual infusion chamber and first through fourth fluid lines. The dualinfusion chamber has a first chamber not fluidly coupled to the secondchamber. The first fluid line is fluidly coupled to the first chamberand is for providing an irrigating fluid to the first chamber. Thesecond fluid line is fluidly coupled to the first chamber and is forproviding the irrigating fluid to a surgical device. The third fluidline is fluidly coupled to the second chamber and is for providing theirrigating fluid to the second chamber. The fourth fluid line is fluidlycoupled to the second chamber and is for providing the irrigating fluidto the surgical device.

In another aspect, the present invention is a surgical cassetteincluding an infusion chamber and a fluid line. The infusion chamber hasan upper surface and a lower surface. The fluid line is fluidly coupledto the infusion chamber and is for providing an irrigating fluid to theinfusion chamber. The infusion chamber has an opening disposed near thelower surface for the fluid line.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and forfurther objects and advantages thereof, reference is made to thefollowing description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a schematic diagram illustrating infusion control in anophthalmic microsurgical system;

FIG. 2 is a schematic diagram illustrating infusion control andirrigation control in an ophthalmic microsurgical system;

FIG. 3 is a front, perspective view of a preferred surgical cassette foruse in the ophthalmic microsurgical system of FIGS. 1 and 2; and

FIG. 4 is a front, perspective, partially fragmentary view of a dualinfusion chamber of the surgical cassette of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the present invention and their advantagesare best understood by referring to FIGS. 1-4 of the drawings, likenumerals being used for like and corresponding parts of the variousdrawings. As shown in FIG. 1, ophthalmic microsurgical system 10includes a pressure cuff 12; an infusion source 14; a dual infusionchamber 16 having a chamber 16 a and a chamber 16 b; fluid level sensors18 and 20; a flow sensor 22; filters 24 and 26; a surgical device 29; acomputer or microprocessor 28; gas manifolds 30 and 32; a pressurizedgas source 34; proportional solenoid valves 36, 38, and 40; “on/off”solenoid valves 42, 44, 46, 48, 50, 52, 54; actuators 56, 58, 60, and62; and pressure transducers 64, 66, and 68. Dual infusion chamber 16;fluid level sensors 18 and 20; portions of infusion fluid lines 70, 72,74, 76, 78, and 80; and portions of gas lines 84 and 86 are preferablydisposed in a surgical cassette 27. Infusion source 14; dual infusionchamber 16; flow sensor 22; filters 24 and 26; and surgical device 29are fluidly coupled via infusion fluid lines 70-80. Infusion source 14,dual infusion chamber 16, gas manifolds 30 and 32; pressurized gassource 34; and actuators 56, 58, 60, and 62 are fluidly coupled via gaslines 82, 84, 86, 88, 90, 92, 94, and 96. Infusion source 14; fluidlevel sensors 18-20; flow sensor 22; microprocessor 28; proportionalsolenoid valves 36-40; on/off solenoid valves 42-54; actuators 56-62;and pressure transducers 64-68 are electrically coupled via interfaces100, 102, 104, 106, 108, 110, 112, 114, 116, 118, 120, 122, 124, 126,128, 130, and 132.

Infusion source 14 is preferably a flexible infusion source. As shownbest in FIGS. 3-4, dual infusion chamber 16 is preferably formed on arear surface 27 a of surgical cassette 27. Surgical cassette 27preferably also has a top surface 27 b and a bottom surface 27 c.Chambers 16 a and 16 b are preferably separated by a divider 16 c, andchambers 16 a and 16 b are not fluidly coupled. Dual infusion chamber 16preferably also has an upper surface 16 d and a lower surface 16 e. Asshown best in FIGS. 1-2, chamber 16 b has an opening 226 disposed on ornear lower surface 16 e for fluid line 74, and chamber 16 a has anopening 228 disposed on or near lower surface 16 e for fluid line 72. Asused in the context of the preceding sentence, “near” preferably meanscloser to lower surface 16 e than to a transverse plane passing througha midpoint between lower surface 16 e and upper surface 16 d, and “near”more preferably means closer to lower surface 16 e than to a transverseplane passing through a point one quarter of the distance from lowersurface 16 e and three quarters of the distance from upper surface 16 d.Fluid level sensors 18 and 20 may be any suitable device for measuringthe level of fluid in infusion chambers 16 a and 16 b, respectively.Fluid level sensors 18 and 20 are preferably capable of measuring thelevel of fluid in infusion chambers 16 a and 16 b in a continuousmanner. Flow sensor 22 may be any suitable device for measuring the flowrate of fluid within fluid line 80. Flow sensor 22 is preferably anon-invasive flow sensor. Filters 24 and 26 are hydrophobicmicro-bacterial filters. A preferred filter is the VERSAPOR® membranefilter (0.8 micron) available from Pall Corporation of East Hills, NewYork. Microprocessor 28 is capable of implementing feedback control, andpreferably PID control. Surgical device 29 may be any suitable devicefor providing surgical irrigating fluid to the eye but is preferably aninfusion cannula, an irrigation handpiece, or and irrigation/aspirationhandpiece. The portions of fluid lines 70-80 disposed in surgicalcassette 27, and the portions of gas lines 84-46 disposed in surgicalcassette 27, may be any suitable line, tubing, or manifold fortransporting a fluid but are preferably manifolds integrally molded intosurgical cassette 27.

In operation, fluid lines 70, 72, and 74; chambers 16 a and 16 b; fluidlines 76, 78, and 80; and surgical device 29 are all primed with asurgical irrigating fluid 140 by pressurizing infusion source 14.Surgical irrigating fluid 140 may be any surgical irrigating fluidsuitable for ophthalmic use, such as, by way of example, BSS PLUS®intraocular irrigating solution available from Alcon Laboratories, Inc.

The pressurizing of infusion source 14 is preferably performed bypressure cuff 12. More specifically, microprocessor 28 sends a controlsignal to open solenoid valve 42 via interface 106 and to close solenoidvalves 44 and 46 via interfaces 108 and 110, respectively.Microprocessor 28 also sends a control signal to open proportionalsolenoid valve 40 via interface 104 so that manifold 30 supplies theappropriate amount of pressurized air to actuate pressure cuff 12.Pressure transducer 68 senses the pressure within gas line 82 andprovides a corresponding signal to microprocessor 28 via interface 126.Solenoid valves 48-54 are initially open so that manifold 32 providespressurized air to actuate actuators 56-62 to close fluid lines 72-78.Microprocessor 28 sends control signals to close solenoid valves 48-54via interfaces 114-120. The closing of solenoid valves 48-54 actuatesactuators 56-62 to open fluid lines 72-78. After all chambers and fluidlines are primed, microprocessor 28 closes actuators 56-62 and thusfluid lines 72-78. Alternatively, the pressuring of infusion source 14may be performed solely via gravity.

After priming, a user then provides a desired intraocular pressure tomicroprocessor 28 via an input 134. Input 134 may be any suitable inputdevice but is preferably a touch screen display or physical knob.Chamber 16 b is preferably the initial active infusion chamber.Microprocessor 28 sends appropriate control signals to open solenoidvalve 44 and to open proportional solenoid valve 36 (via interface 100)to provide an appropriate level of pressurized air to chamber 16 b.Pressure transducer 64 senses the pressure within gas line 84 andprovides a corresponding signal to microprocessor 28 via interface 124.Microprocessor 28 also sends an appropriate control signal to openactuator 60 and thus fluid line 78. Chamber 16 b supplies pressurizedfluid 140 to the eye via fluid lines 78 and 80 and surgical device 29.Flow sensor 22 measures the flow rate of fluid 140 and provides acorresponding signal to microprocessor 28 via interface 132.Microprocessor 28 calculates a predicted intraocular pressure using thesignal from flow sensor 22 and empirically determined impedanceinformation of microsurgical system 10. Microprocessor 28 then sends anappropriate feedback control signal to proportional solenoid valve 36 tomaintain the predicted intraocular pressure at or near the desiredintraocular pressure during all portions of the surgery.

Fluid level sensor 20 continuously monitors the decrease in the level offluid 140 in chamber 16 b during surgery and provides a correspondingsignal to microprocessor 28 via interface 130. Microprocessor 28performs adjustments to the air pressure provided to chamber 16 b toaccommodate for the difference in fluid head height as the level offluid 140 decreases. When the level of fluid 140 in chamber 16 b reachesa bottom limit level, microprocessor 28 closes solenoid valve 44 andactuator 60 and opens solenoid valve 46 and actuators 58 and 62. Chamber16 a is now the active infusion chamber. Microprocessor 28 sends anappropriate control signal to proportional solenoid valve 38 viainterface 102 to provide an appropriate level of pressurized air tochamber 16 a. Pressure transducer 66 senses the pressure within gas line86 and provides a corresponding signal to microprocessor 28 viainterface 122. Chamber 16 a supplies pressurized fluid 140 to the eyevia fluid lines 76 and 80 and surgical device 29. Flow sensor 22measures the flow rate of fluid 140 and provides a corresponding signalto microprocessor 28 via interface 132. Microprocessor 28 calculates thepredicted intraocular pressure as described above and the sends anappropriate feedback signal to proportional solenoid valve 38 tomaintain the predicted intraocular pressure at or near the desiredintraocular pressure during all portions of the surgery. Microprocessor28 closes actuator 58 and fluid line 74 once chamber 16 b is refilledwith fluid 140.

Fluid level sensor 18 continuously monitors the decrease in the level offluid 140 in chamber 16 a during surgery and provides a correspondingsignal to microprocessor 28 via interface 128. Microprocessor 28performs adjustments to the air pressure provided to chamber 16 a toaccommodate for the difference in fluid head height as the level offluid 140 decreases. When the level of fluid 140 in chamber 16 a reachesa bottom limit level, microprocessor 28 switches chamber 16 b to activeinfusion, makes chamber 16 a inactive, and refills chamber 16 a withfluid 140 via fluid line 72. This cycling between chambers 16 b and 16 acontinues throughout the surgery.

Infusion source 14 is preferably monitored via a fluid level sensor (notshown) capable of providing a signal to microprocessor 28 via interface112 when source 14 reaches a near empty limit. Chambers 16 a and 16 balso preferably each have a volume that enable infusion source 14 to beexchanged, when near empty, without interrupting the surgical procedure.More specifically, chambers 16 a and 16 b preferably each have a volumeof about 30 cc. Such volume allows about two minutes for a near emptyinfusion source 14 to be exchanged during conditions of maximum flow(e.g. core vitrectomy). In addition, since fluid lines 72 and 74 arefluidly coupled to chambers 16 a and 16 b, respectively, at or nearlower surface 16 e, once infusion source 14 is exchanged all air bubbleswithin fluid lines 70, 72, and 74 will be automatically “scrubbed out”as the inactive chamber 16 a or 16 b refills, without the need forre-priming.

In the case of failure of either of chambers 16 a or 16 b,microprocessor 28 can preferably continue surgery with only one activechamber. In the case of failure of both chambers 16 a and 16 b,microprocessor 28 can preferably continue surgery using only infusionsource 14.

FIG. 2 shows a modified ophthalmic microsurgical system 10 a.Microsurgical system 10 a is similar to microsurgical system 10 exceptthat it has an irrigation system in addition to the infusion systemdescribed above for system 10. More specifically, system 10 a isidentical to system 10 except that system 10 a also includes anirrigation source 200; fluid lines 202 and 206; gas lines 208 and 216;solenoid valves 210 and 218; actuators 214 and 222; electricalinterfaces 212 and 220; and a surgical device 224. As shown in FIG. 2,irrigation source 200 is pressurized solely by gravity. The portions offluid lines 202 and 206 disposed in surgical cassette 27, and theportions of gas lines 208 and 216 disposed in surgical cassette 27, maybe any suitable line, tubing, or manifold for transporting a fluid butare preferably manifolds integrally molded into surgical cassette 27. Aswill be appreciated by one of ordinary skill in the art, microsurgicalsystem 10 a allows surgical irrigating fluid 140 to be delivered tosurgical device 29 via fluid line 80 (infusion), and surgical irrigatingfluid 140 to be delivered to surgical device 224 via fluid line 206(irrigation), independently. Microprocessor 28 can calculate flowinformation for fluid 140 within fluid line 206 by continuouslymonitoring the volumetric change of fluid inside chamber 16 b, asindicated by fluid sensor 20.

From the above, it may be appreciated that the present inventionprovides an improved method of controlling intraocular pressure with amicrosurgical system. The present invention is illustrated herein byexample, and various modifications may be made by a person of ordinaryskill in the art. For example, while the present invention is describedabove relative to controlling intraocular pressure in an ophthalmicmicrosurgical system, it is also applicable to controlling pressurewithin the operative tissue during other types of microsurgery.

It is believed that the operation and construction of the presentinvention will be apparent from the foregoing description. While theapparatus and methods shown or described above have been characterizedas being preferred, various changes and modifications may be madetherein without departing from the spirit and scope of the invention asdefined in the following claims.

1. A surgical cassette, comprising: a dual infusion chamber forreceiving an irrigating fluid from a source external to said cassette,said dual infusion chamber disposed within an interior of said surgicalcassette, said dual infusion chamber having a first chamber and a secondchamber, each of said first chamber and said second chamber having avolume sufficient to hold an amount of irrigating fluid to enable saidsource of irrigating fluid to be exchanged without interrupting asurgical procedure, said first chamber not fluidly coupled to saidsecond chamber; a first fluid line fluidly coupled to said first chamberfor providing said irrigating fluid to said first chamber; a secondfluid line fluidly coupled to said first chamber for providing saidirrigating fluid to a surgical device; a third fluid line fluidlycoupled to said second chamber for providing said irrigating fluid tosaid second chamber; and a fourth fluid line fluidly coupled to saidsecond chamber for providing said irrigating fluid to said surgicaldevice.
 2. The surgical cassette of claim 1 wherein said first chamberand said second chamber are separated by a divider.
 3. The surgicalcassette of claim 1 wherein said volume is sufficient for about twominutes of said surgical procedure during a condition of maximum flow.4. The surgical cassette of claim 1 wherein said volume is about 30 cc.